1. Field of the Invention
This invention generally relates to a pressure relief valve and, more particularly, to a normally-closed valve which opens when a pressurized fluid exceeding a threshold pressure flows therethrough.
2. Description of Related Art
Pressure relief valves are known for venting surge pressures in a pipeline, or for maintaining pipeline pressure. A typical relief valve employs a rubber sleeve and an externally-mounted actuator for pinching the sleeve closed. The actuator includes a spring loaded into a cylinder extending normally to the sleeve, as well as a tension-adjusting mechanism for the spring. When the pressure of a fluid flowing through the valve exceeds the spring tension, the sleeve opens.
Although generally satisfactory for its intended purpose, the external actuator for such a relief valve is a multi-part, complex arrangement subject to environmental corrosion and valve failure. The external actuator occupies space which, in some applications, may not be available. The external actuator contributes to an increased weight, size and cost, all factors which are better avoided.